In recent years, MIMO (Multiple-Input Multiple-Output) has received attention, as a system for implementing fast transmission using limited frequency bands effectively.
MIMO is a system where multi antennas is used in both transmission and reception, and independent signals are transmitted and received at the same time in the same band using multi eigenvectors. Using MIMO enables increases in transmission capacity without increasing the frequency band.
In this system, in order to improve the throughput, a transmission apparatus controls parameters of adaptive modulation processing and so on based on the reception electric field strength of the entire system estimated in a reception apparatus. For example, the transmission apparatus performs processing for increasing the modulation level of M-ary modulation when the reception electric field strength of the entire system is higher than a predetermined threshold. This is the same as in conventional MIMO.
However, there are cases that the reception electric field strength varies among channels in communications using multi channels, such as MIMO. When the adaptive modulation processing is performed based on the reception electric field strength of the entire system in MIMO, the modulation level is increased even when the reception electric field strength of a single channel is extremely larger than those of other channels. As a result, the reception quality deteriorates in a large number of channels with low reception electric field strength.